1. Technical Field
The present invention relates to: an image processing apparatus, an image reading apparatus, an image forming apparatus, an image processing method, and a computer program performing a cropping process on a document image containing a text or a graphic; and a recording medium storing the computer program.
2. Description of Related Art
In the prior art, a technique is known that a part of an image (a document image) obtained by reading a document is identified and then the identified part is cropped alone. Another technique is also known that the edges of such a document image are calculated and then the entire document image is cropped.
For example, in a reading control system described in Japanese Patent Application Laid-Open No. 2007-174479, an image reading apparatus reads a document in an achievable maximum area, then information indicating the sheet size of the document is received from a user, and then an area having the sheet size indicated by the received information is calculated as a crop box in the read-out document image. Specifically, in the reading control system described in Japanese Patent Application Laid-Open No. 2007-174479, in the image acquired by reading the document in the achievable maximum area, a part having an image density exceeding a threshold having been set up in advance is detected as an area where a significant image is present. Then, a shape and an area that agree with the sheet size of the document are calculated as the crop box. For example, when the area of the crop box is adopted such that the area where a significant image is present should be located in the center of the area of the crop box, the image of the document is displayed appropriately even when the document has been read in a position deviated from an appropriate alignment.
Further, in an image input apparatus described in Japanese Patent Application Laid-Open No. 2007-201752, size information concerning the horizontal and vertical lengths of each standard sheet size is stored in advance. Next, image data with a given size is read from a document, and then the size of the document part is calculated from the read-out image data. Then, in the image input apparatus described in Japanese Patent Application Laid-Open No. 2007-201752, the calculated size of the document part is compared with the size information, and finally the image data is cropped into a sheet size closest to the size of the document part.